Formoterol exhibits pharmacological activities such as relaxation of bronchial smooth muscle through its selective actions on .beta.-receptors in the sympathetic nervous system (see Japanese Patent Publication No. 9542/1984), and thus has been widely used in the treatment of chronic obstructive respiratory diseases, particularly bronchial asthma, with the purpose of ameliorating the dyspnea of patients with respiratory stenosis. Up to this time, formoterol has been orally administered in the form of tablets and dry syrups. In general, however, the oral administration of a remedy for a disease to be treated through the excitation of .beta.-receptors often failed in suppressing or preventing attacks due to bronchial asthma or the like at night.
With respect to an integral transdermal system comprising an impermeable backing, a adhesive layer and a release liner, there has recently been disclosed a technique of forming the pressure-sensitive adhesive layer out of a mixture comprising a drug, a pressure-sensitive adhesive and a fluidity enhancer consisting of eucalyptol having a purity of 70% to thereby enhance the release of the drug from the system (see Japanese Patent Laid-Open No. 311017/1989).
Further, a multilayer patch has been disclosed, which comprises a cover sheet impermeable to the components of the reservoir layer which will now be described, a reservoir layer which is made from a mixture of an adhesive polymer with an optionally crosslinked block copolymer of styrene, an alkadiene and, if necessary, an alkene capable of being fed with an active substance, may be provided with an additional adhesive film at need, and contains an active substance capable of permeating the skin, a skin-permeation accelerator and, if necessary, a medical assistant, and a release film (see Japanese Patent Laid-Open No. 78615/1990).
However, the incorporation of formoterol into the pressure-sensitive adhesive layer of the above integral transdermal system or the reservoir layer of the above multilayer patch was disadvantageous in that the stability of formosterol was often problematic and that the high affinity of formoterol for the pressure-sensitive adhesive was causative of lowering the release of formoterol into the skin or hindering the extraction thereof in quantitative analysis.